Pressure-induced superhard phase of C60

The superhard phase of C-60 has been found at non-hydrostatic high pressure 22.4 GPa at room temperature by in situ X-ray diffraction study, This phase exists at the pressure up to 32.7 GPa. At the higher pressure there is a random network of fullerene molecules. The crystal structure has been determined by Rietveld analysis of the high-pressure diffractogram. The best fit profile has been simulated by a 3D polymerized structure with (2 + 2) cycloaddition along a and b axes and (3 + 3) type of cycloaddition along the space diagonal of orthorhombic structure. The bulk modulus B-0 is tentatively determined by the compressibility up to 32.7 GPa, and its value is approximately equal to 530 +/- 80 cpa, (C) 2001 Published by Elsevier Science Ltd.